Sevier County Sheriff's Office(KNOXVILLE, Tenn.) -- Brett Knight, a 45-year-old Utah native, has been arrested in Knoxville, Tenn., on suspicion of murdering a renowned horse riding instructor a little more than two weeks ago, according to the U.S. Marshals.

After spurring a nationwide search during which police said Knight was "armed, volatile and extremely dangerous," he was found inside a house in Seymour County, Tenn., and taken into custody Wednesday morning by U.S. Marshals and the Sevier County Special Operations Response Team, according to a statement by the Marshals. Police recovered two handguns during the arrest.

Authorities suspect that Knight shot at Ross Reisner and his partner, Kevin Murray, on the evening of Sept. 24, as the longtime couple was sitting on a couch inside Reisner's Long Island, N.Y., home in Suffolk County. Reisner died from the gun shots fired by a high-caliber weapon, according to police, while Murray was left grazed by a bullet.

A neighbor who has lived near the home where Knight was arrested for 25 years told ABC News that for the last six or seven months, he spotted what looked like sheets covering up the windows.

"I drive by there every day," Nathan Randles said. "They always had their windows covered up."

Randles described the house as a small, gray, three-bedroom, two-bath home. He had never interacted with the owners of the home, but estimated they moved in roughly a year ago.

Ian Reisner, Ross Reisner's brother, told ABC News that Knight and his brother were friends for nearly 20 years.

Knight lived in an apartment inside of Ross' home two years ago, but was evicted by the couple for erratic behavior, Ian said.

Just months before Ross' murder, someone sent a dead bird to the horse trainer's home, Ian said. Court records obtained by ABC News showed that Knight was terminated from a top position at American Express in 2009, leading him to file a lawsuit alleging he was discriminated against by his managers. Knight claimed that once his manager discovered he was gay via an HIV diagnosis, he began to be estranged from the work community.

However, Knight and the defendants agreed to discontinue the lawsuit in 2011, according to the court docket.

A former neighbor of Knight's at a New York apartment building in the mid-1990s told ABC News that Knight never showed any signs of suspicious behavior.

"He was a very nice guy," said Linda, 65, who would not disclose her last name. "He was just a young guy building a career."

Ian, speaking on behalf of the family Wednesday evening, expressed relief after Knight's arrest.

"The family is relieved that we are closer to resolution on this tragedy," an e-mailed statement read.

Police have not disclosed Knight's location, or when or where Knight will be arraigned.